1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the semiconductor device, and more particularly, it relates to a semiconductor device formed with a gate electrode in a groove and a method of fabricating the semiconductor device.
2. Description of the Background Art
A semiconductor device formed with a gate electrode in a groove is known in general. A conventional semiconductor device includes an n−-type drain drift region (second drain region) on an n+-type buried region (first drain region). This drain drift region is formed with a plurality of grooves and the grooves are formed with gate electrodes through insulating films. A p-type base region is formed between the plurality of grooves of the conventional semiconductor device, and an n+-type source region is formed on the base region. The drain drift region of the conventional semiconductor device is formed with drain lead-out regions laterally of the plurality of grooves. Since a reverse bias voltage is applied to a p-n junction portion between the drain drift region and the base region when a voltage is applied to source/drain regions, the conventional semiconductor device is constituted such that a depletion layer is formed on the p-n junction portion. Thus, an electric field formed below the source region is relaxed by the depletion layer of the p-n junction portion.
In the aforementioned conventional semiconductor device, however, electric field concentration disadvantageously occurs in the vicinity of outer corner portions of lower ends of the outermost grooves when a voltage is applied to the source/drain regions, since no base region is formed outside of the outermost grooves (on sides closer to the drain lead-out regions) among the plurality of grooves formed with the gate electrodes. Therefore, the breakdown voltage of the semiconductor device is disadvantageously reduced due to the electric field concentration.